Ceramic heater devices are well known in the art. The ceramic heater tip of a glow plug is generally a cylindrical element which is brazed to a metallic body or housing. However, the brazing is susceptible to failure due to the high combustion chamber pressures and temperature.
Further, such cylindrical ceramic heater tips become caked with a carbon coating during normal use. If service is required for the glow plug, the glow plug must be extracted from the cylinder head. The carbon build-up on the ceramic tip tends to lock the ceramic tip in the cylinder head. As the repairer removes the metallic body, the ceramic tip occasionally becomes dislodged from the metallic body and remains in the cylinder head, which is highly undesirable.
Attempts have been made to address this problem by improving the mechanical joint structure for positively retaining the ceramic heating tip within the bore of the body of the glow plug, as disclosed in U.S. Pat. No. 5,084,607. However, this proposed design requires additional precision parts to be manufactured, and thus increases the cost of the glow plug.